Software and Tools

7-Zip Script Tools for ArcGIS
You can download the tools discussed in my blog post “A Script Tool for Unzipping Files in ArcGIS” by clicking on the link below. More information  about these tools is available in the blog post. [Zip, 8Kb].

Ecology Presentations and Posters

Presentation: Using GIS to Automate Distribution Models for New World Trees
The following is a link to a PowerPoint Show (*.ppsx) file containing the slides from my presentation [PPSX, 7.6Mb] at the 2011 esri User Conference in San Diego.

The conference abstract is also below:

This presentation will show how ArcGIS Modelbuilder, Python and the geoprocessing environment were instrumental in automating the data processing and analysis workflows for a project to create over 200,000 temperate and tropical plant species distribution models from the largest single-database of species occurrence records spanning the entire New World. The modeling results are helping define the spatial distributions of some tree species that were not previously understood, identify potential ICUN red-list candidates for species with critically small spatial distributions, and better understand how climate and climate change influence species range sizes, abundance, and extinction risk. This presentation will also discuss future data dissemination plans, and how practitioners can overcome the problems associated with combining multiple datasets of spatially referenced ecological data so that the science and conservation communities can effectively combine datasets to help analyze ecological patterns at large spatial scales and understand how species may respond to climate change.

Poster: Does the climatic variability hypothesis explain the longitudinal range size gradient in North American trees?
From the 96th ESA Annual Meeting, Austin, Texas: View [PDF, 1.3MB]

Latitudinal range size gradients have long been documented for North American tree species, and recent work has shown that latitudinal range size gradients are consistent with the climatic variability hypothesis. While longitudinal range size gradients for North American tree species have also been documented, it is uncertain whether this pattern can also be explained by the climatic variability hypothesis. In this study, I evaluated whether the longitudinal gradient in geographic range sizes can be explained by climatic variability.

Using digital representations of range maps from E.L. Little’s Atlas of North American Trees, information from the USDA Plant Database, and climatic data from WorldClim, I performed a principal components analysis on 19 bioclimatic variables extracted from the geographic limits of each species’ range, to ascertain how geographic range size fluctuated with multidimensional climatic variability. I also used the PCA results to identify which bioclimatic factors most influenced climatic variability over geographic ranges, and tested how those combined factors varied with range size.

Results show that variation in PCA 1 was driven by factors related to temperature, while variation in PCA 2 was driven by factors related to precipitation. PCA 1 exhibited a moderately statistically significant negative relationship with range size for all species (r2= 0.3675, p = 0.0). The pattern was somewhat weaker for gymnosperms (r2= 0.2483, p < 0.0001) but stronger for angiosperms (r2= 0.4222, p < 0.0001). PCA 2 showed only a moderately statistically significant positive relationship with range size for gymnosperms (r2= 0.2127, p < 0.0001). A regression model using five bioclimatic factors most influential in determining climatic variation across species’ ranges was statistically significant, explaining 66% of the variation in range size (r2= 0.66, p < 0.0001).

This study shows that the longitudinal range size gradient for North American trees is consistent with the climatic variability hypothesis. Species with small geographic ranges sample a climatic space with more variable temperature ranges and precipitation regimes than large range species. The results also seem to contradict the notion that species’ geographic range sizes are driven by whether they are climatic specialists or generalists. Large range species may not be climatic generalists; they may be simply exploiting a more homogenous climate.

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